Stockholders' Equity - Schedule of Quarterly Cash Dividends to Common Stockholders (Detail) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013 Q4 2013 Declaration [Member]	Sep. 30, 2014 Q4 2013 Declaration [Member]	Mar. 31, 2014 Q1 2014 Declaration [Member]	Sep. 30, 2014 Q1 2014 Declaration [Member]	May 31, 2014 Q2 2014 Declaration [Member]	Sep. 30, 2014 Q2 2014 Declaration [Member]	Sep. 30, 2014 Q3 2014 Declaration [Member]	Sep. 30, 2014 Q3 2014 Declaration [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend record date						Dec. 20, 2013		Mar. 20, 2014		Jun. 20, 2014		Sep. 29, 2014
Dividend payable date						Jan. 03, 2014		Apr. 01, 2014		Jul. 01, 2014		Oct. 06, 2014
Cash dividends declared	$ 0.21	$ 0.20	$ 0.62	$ 0.40	$ 0.20		$ 0.20		$ 0.21		$ 0.21